Establishment of a novel experimental animal model for the treatment of tibial segmental bone defects in juvenile sheep.

Segmental long bone defects present a significant clinical challenge as critical-size defects cannot heal spontaneously. Most studies focus on adult bone defects, with limited research on pediatric cases. To enhance the study of bone defects in children, we established a juvenile sheep bone defect model. Juvenile small-tailed Han sheep were used to create a 2 cm tibial bone defect, stabilized with a plate and screws. Tissue-engineered bone scaffolds were implanted at the defect site, and the limb was immobilized with a plaster cast for 3 months. Sheep were euthanized at 3 and 6 months post-surgery, and tibiae were examined using X-ray, microCT, and histological staining. Tibial defect models were established in 7 sheep, with 2 euthanized at 3 months and 5 at 6 months. X-ray revealed cortical bridging. MicroCT and histological staining showed new bone distribution, with the 6-month group demonstrating increased bone formation and bridging at the scaffold center. There was no significant difference in longitudinal growth rates between the operated and contralateral tibiae. We developed a reproducible model for juvenile tibial segmental defects in sheep, providing a robust basis for studying pediatric long bone segmental defects.